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Video Signal Basics: Resolution, Frame Rate and Why the Picture Drops Out

What the numbers on a video signal mean, why a laptop and a screen sometimes refuse to talk, and where in the chain to look when they do.

~7 min read · Updated August 2026 · By the Stage Supply team

In this guide:The numbers · The handshake · HDCP · Diagnosis · Picks · FAQ

Video at events fails differently from audio. Audio degrades: it gets quieter, or noisier, or distorted, and you can hear the problem. Video either works or produces nothing at all, usually accompanied by a laptop insisting everything is fine.

Knowing what the signal is made of tells you where to look.

Resolution and frame rate

**Resolution** is the pixel count, quoted as width by height or by shorthand. 1920 by 1080 is 1080p or HD. 3840 by 2160 is 4K, sometimes called UHD.

**Frame rate** is how many complete images per second, and in the UK the broadcast-derived rates are 25 and 50, while computer sources commonly output 60. That mismatch matters more than people expect, because a device set to one and a source running the other can produce judder, or nothing.

**Progressive and interlaced**, the p and i, describe whether each frame is drawn complete or in two halves. Modern equipment is overwhelmingly progressive, and interlaced formats mostly appear in broadcast chains.

The combination of resolution and frame rate determines bandwidth, and bandwidth determines what cable and converter you need. That is the subject of video conversion.

EDID, and why nothing appears

When you plug a source into a display, they negotiate. The display sends a block of data describing what it can accept, called EDID, and the source picks a format from that list.

This is why a laptop plugged into a projector sometimes shows nothing at all. If the negotiation fails, or the source reads the wrong capabilities, it may output a format the display cannot show, or refuse to output at all.

  • Plug the display in before starting the source, so the information is there to read.
  • If nothing appears, unplug and replug, which forces a new negotiation.
  • Devices in the middle, such as switchers and converters, all participate. Each one is another chance for it to go wrong.
  • EDID managers exist precisely for this, and they present a fixed, known capability to the source so the negotiation cannot go astray.

The event answer

Set the source to a fixed, known resolution and frame rate rather than letting it choose. Guessing is what negotiation does, and on a show you want certainty.

Copy protection, and the black screen

HDCP is content protection, and it is the other common cause of a blank screen. Protected content, from streaming services and some players, will refuse to display if any device in the chain does not support it.

The symptom is distinctive: everything else works, and one particular source gives a black screen or an error, often part way through. If a client wants to play a commercial film or a streaming service through an event system, raise it in advance, because it is a rights and equipment issue rather than a fault to fix on the day.

A running order for a picture that will not appear

  • Is the display on the correct input? This is the answer more often than anything else.
  • Is the source outputting? Check the laptop display settings, and whether it is mirroring or extending.
  • Replug to force a new handshake.
  • Bypass the middle. Plug the source directly into the display. If that works, the fault is in a converter, switcher or cable.
  • Try a known good cable, then a known good converter.
  • Check the format. If the source is set to something exotic, set it to 1080p at 60 and try again.

Frequently asked questions

Why does my laptop show no picture on the projector?

Usually the handshake, or the laptop set to mirror rather than extend, or the projector on the wrong input. Replug to force a new negotiation and check the display settings.

What resolution should I run at an event?

1080p is still the safe default for live events, because everything supports it and the bandwidth is manageable. Use 4K only where the content and the whole chain justify it.

What is EDID?

The data a display sends to a source describing what formats it accepts. The source picks from that list, so a bad or missing EDID means the source guesses, and the guess may be wrong.

Why does one video file play and another shows black?

Often content protection. Protected content requires every device in the chain to support HDCP, and one that does not produces a black screen while everything else works normally.